When a gas turbine is started, the volume, temperature and velocity of its exhaust gases very quickly reach their maximums. The exhaust systems of gas turbines are employed to provide the heat required for the operation of heat recovery steam boilers and such systems typically have a bypass into which the hot gas stream is diverted when, for one example, the cogenerating system is to be placed temporarily out of service.
Means are provided to control the flow to the steam boiler and to divert the exhaust stream into the bypass and such may be a hinged diverter blade operable to shift the flow from either system to the other, see Ser. No. 055,594, filed May 29, 1987, now U.S. Pat. No. 4,821,507, and Ser. No. 200,504 filed May 31, 1988 now U.S. Pat. No. 4,823,836, or one or more louver dampers or a combination of louver and guillotine dampers may be positioned in the bypass and one or more louver dampers or a combination of louver and guillotine dampers may be incorporated in the exhaust system between the bypass and the steam boiler.
Because of the sudden build up of the temperature in gas turbine exhaust systems, it is necessary for louver dampers to be able to accommodate thermal expansion forces. In Ser. No. 055,594, a diverter blade is disclosed having that capacity and in Ser. No. 200,504 effective leaf spring seals are provided which are installed in a manner accommodative of thermal expansion forces in conjunction both with diverter blades and louver dampers.
In the manufacture of louver dampers, the weight of the louver blades is held down by utilizing relatively thin metal stock and by a construction providing a suitably reinforced blade and ported to enable interior surfaces and surfaces upstream when the damper is closed to be evenly heated in order to avoid blade distortions.